1. Technical Field
The present invention relates to a liquid discharge apparatus, a circuit substrate, and an integrated circuit device.
2. Related Art
As a liquid discharge apparatus, such as an ink jet printer for discharging ink to print an image or a document, a liquid discharge apparatus using a piezoelectric element (for example, a piezo element) is known. A piezoelectric element is provided corresponding to each of a plurality of nozzles in the head unit, each of the piezoelectric elements is driven according to a driving signal, and accordingly, a predetermined amount of ink (liquid) is discharged from the nozzle at a predetermined timing to form dots. Since the piezoelectric element is a capacitive load, such as a capacitor, in terms of electricity, it is necessary to supply a sufficient current in order to operate the piezoelectric element of each of the nozzles.
Therefore, in the above-described liquid discharge apparatus, a configuration in which the driving signal amplified by an amplifying circuit is supplied to a head unit (ink jet head) to drive the piezoelectric element, is employed. As a driving circuit for generating a driving signal, there is a device which performs current amplification of a source signal before amplification with a class AB amplifier or the like, but since energy efficiency is not excellent, in recent years, a driving circuit using a class D amplifier has been suggested (refer to JP-A-2010-114711). In addition, a driving circuit (division power source type driving circuit) that generates a driving signal by selecting a transistor to perform a switching operation from a plurality of transistors of which power source voltages are different according to the voltage of the driving signal has also been suggested (refer to JP-A-2014-184569).
However, in order to obtain discharge accuracy (in order to make the output waveform highly precise), the class D amplifiers for the ink jet heads are required to have an oscillation frequency (1 to 8 MHz) 20 times higher than that of the class D amplifiers for audio, and thus, noise, such as an electromagnetic interference (EMI) is likely to be generated. In contrast, the division power source type driving circuit has high energy efficiency and is capable of suppressing the generation of EMI. However, when the driving circuit for the ink jet head is integrated, a driving circuit that operates at a high voltage and a control circuit that operates at a low voltage coexist in the same IC chip. Therefore, the operation of the low-voltage circuit is affected by the noise generated in the high-voltage driving circuit, and the discharge of the ink may be disturbed.